"Workspace Owners can apply for Corporate Export. This lets you export all messages (including DMs and private channels), but only if your company has legal or compliance requirements and Slack approves the request. Once approved, exports are scheduled and delivered automatically."
So they have the tech built, you just aren't allowed to use it. Who would use this piece of garbage?
In some cases, as Slack says, there may be a legal mandate to log employee conversations, but in other situations there may be legal restrictions on reading employee-to-employee conversations. That all probably varies by jurisdiction.
And then you have more complicated situations, like companies that use Slack to offer tech support to their customers, or random open-source projects or local volunteer projects using Slack. They might pay for a business license for various features, but it's probably not clear to every member that that would mean whoever set up the Slack account should get to read everyone else's correspondence.
You also want some kind of safety check to make sure that a random IT guy who set up the Slack system at a small company isn't reading through people's DMs and private channels to stalk people or access confidential information.
(But I would also start making backups regularly, because who knows if how long this would last)